Summ10Ex2

Summ10Ex2 - "Grade or Education" =1 CHEM 2261/01...

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Unformatted text preview: "Grade or Education" =1 CHEM 2261/01 Summer 10 Exam 2 Chapters 4-6 1. Using ethyne as the starting material, pick the choice which CORRECTLY describes how the compound with the structure shown below can be prepared. o First steps: 1. NaNHZ, 2. CHgBr; Next step: Na/NH3; Final steps: 1. NaNHZ, 2. CH3CHZBr B. First steps: 1. NaNHZ, 2. CHgBr; Next step: HZ/Lindlar catalyst; Final steps: 1. NaNHZ, 2. CH3CHzBF C. First steps: 1. NaNHZ, 2. CHgBr; Next steps: 1. NaNHZ, 2. CH3CHZBr; Final step: H2 and Pd/C D. First steps: 1. NaNHZ, 2. CHgBr; Next steps: 1. NaNHZ, 2. CH3CHZBr; Final step: Na/NH3> E. First steps: 1. NaNHZ, 2. CHgBr; Next steps: 1. NaNHZ, 2. CH3CHZBr; Final step: HZ/Lindlar catalyst Rationale: Chapter 6 Problem 43e 2- Figure out whether each of the following pairs of compounds are identical or are enantiomers, diastereomers, or constitutional isomers. Pick the choice which gives the CORRECT relationship between one of these pairs. CIWCI CI/m/CI f1 f2 H Br Br, Br H H Br b1 b2 Hg/AsH3 HsCAH CH 3 CH3 H CH3 H CH3 ©3‘\CH3 (©_.\‘CH3 C1 C2 HSC‘“ H30 d1 d2 H H3C\ / H\ [CH3 /C=C\ /C=C H 0 Br ‘ __ b1 and b2 are identical. 3 N Br h2 CH3 f1 and f2 are identical. A B C. d1 and d2 are enantiomers. D c1 and c2 are diastereomers. E M and h2 are enantiomers. Rationale: similar to Chapter 5 Problem 67 (b,c,d,f,h) 3- Draw out the mechanism for the reaction shown below using curved arrows to depict electron movement. Use the letter "R" to represent the isopentyl group of the alcohol in order to save time. Use your drawing to choose the statetement from the multiple choices which is WRONG about this mechanism. CHECIEH-CHECH-ZOH + CH3C|3=CH2 —> CHECIEH-CHECH-ZO—CIE—CH3 CH3 CH3 CH3 CH3 A. In the second step of this mechanism a lone pair of electrons located on the oxygen atom of the alcohol molecule attacks a tertiary carbocation. This is represented by a curved arrow with its tail at the lone pair of electrons and its point directed toward the positive charge. B. In the first step of this mechanism a hydrogen cation attacks a double bond. This is represented by a curved arrow originating at the hydrogen and pointing toward the double bond. C. In the third step of this mechanism a protonated oxygen atom loses a hydrogen cation. This is represented by drawing a curved arrow which originates at the bond between the oxygen atom and the hydrogen atom being lost. This curved arrow points toward the middle of the positively—charged oxygen atom. D. The second intermediate in this mechanism is an ion containing a positively—charged oxygen atom. E. There are two intermediates and three steps in this mechanism. Rationale: Chapter 4 Problem 14 4- Find the structure(s) of the product(s) of the reaction shown below. Pick the choice which references ALL of the CORRECT reaction products. H\ ,CH3 1. BH3/THF ,C=C\ PRODUCT(S) H30 CH(CH3)2 2. H202, HO- H H H H CH3 OH CH3 OH Ho CH3 Ho CH3 H CH3 CH3 H CH3 H H CH3 CH(CH3)2 CH(CH3)2 CH(CH3)2 CH(CH3)2 1 2 3 4 This reaction produces products 1 , 2 , 3 , and 4 . This reaction produces only product 3 . A B C. This reaction produces only product 4 . D This reaction produces products 2 and 4 . E This reaction produces products 1 and 3 . Rationale: Chapter 5 Problem 93 Figure out what reagents are required to convert the alkene labelled A shown below into the alcohols labelled B , C , and D . Choose the CORRECT statement from the multiple choices. B )V/ _. A \ c OH MOH A Alkene A will react with H20 and H2504 to form alcohol B . B Alkene A will react with: 1. Hg(OAc)2, HZO/THF; followed by 2. NaBH4 to form alcohol D . C. Alkene A will react with: 1. BH3/THF; followed by 2. H202, HO, H20 to form alcohol C. D Alkene A will react with H20 and H2504 to form alcohol D. E Alkene A will react with H20 and H2804 to form alcohol C. Rationale: Chapter 4 Problem 43 Which of the numbered structures shown below is (2R,3R)—2,3—dichloropentane? CH3 CH3 CH3 CH3 Cl H H Cl Cl H H Cl Cl H H Cl H Cl Cl H CHZCH3 CH2CH3 CH2CH3 CH2CH3 1 2 3 4 __ A. 3 __ B. 2 __ C. 4 __ D. None of these structures is correct. E. 1 Rationale: Chapter 5 Problem 88b 7- The compound whose structure is shown in the center of the figure following can be converted into all of the other outer compounds whose structures are shown. Conversion number 1 transforms the center compound into the topmost compound in the figure (see boxed number 1). Conversion number 2 transforms the center compound into the outer compound one position clockwise from the topmost compound, etc. (ie. the conversion numbers are arranged in a clockwise pattern). Use this information to find the multiple choice answer which is WRONG. Br CH—CH—CH CHECHECH-ZOH 2 2 3 1 CH§c|:O:-CH3 CHe—CHZCHe CHEEH—CHS E// r CHECH—CHS CHECH—CHZ IOCH3 \o/ OH A Conversion number 5 can be carried out using Brz and H20. B Conversion number 8 can be carried out using BH3 followed by H202 and base (OH_). C. Conversion number 3 can be carried out using HBr and peroxide. D Conversion number 2 can be carried out using HZ/Pt. E Conversion number 6 can be carried out using acid (H+) and CH3OH. Rationale: similar to Chapter 4 Problem 47 8- a—Farnesene is a dodecatetraene found in the waxy coating of apple skins. Its structure is shown below. What is it's systematic name? / / \\ A (3E,6E)—3,7,11—trimethyl—1,3,6,10—dodecatetraene B. (62,92)—2,6,10—trimethyl—2,6,9,11—dodecatetraene C. (6E,9E)—2,6,10—trimethyl—2,6,9,11—dodecatetraene D (32,62)—3,7,11—trimethyl—1,3,6,10—dodecatetraene E (3E,6E,1OE)—3,7,11—trimethyl—1,3,6,10—dodecatetraene Rationale: Chapter 6 Problem 50 The compound whose structure is shown in the center of the figure below can be converted into all of the other outer compounds whose structures are shown. Conversion number 1 transforms the center compound into the topmost compound in the figure (see boxed number 1). Conversion number 2 transforms the center compound into the outer compound one position clockwise from the topmost compound, etc. (ie. the conversion numbers are arranged in a clockwise pattern). Use this information To find the multiple choice answer which is WRONG. RCH-CH Conversion number 6 can be carried out using 1 equiv. of HBr. Conversion number 4 can be carried out using HZO/HZSO4 + HgSO4. A B __ C. Conversion number 7 can be carried out using excess HBr. D Conversion number 5 can be carried out using disiamylborane followed by HO‘/HZOZ. E __ . Conversion number 8 can be carried out using excess Hz/Pd/C. Rationale: Chapter 6 Problem 29 10- Which of the structures below is/are (S)—2—chlorobutane? CI CI /C---CH /\_/ CH3 ' H 3 CH3 a H ‘ Cl C ci e H H /'\/ CHZCHS H CI CH3 b d f A Only b is (S)—2—chlorobutane. B Only c is (S)—2—chlorobutane. C. Structures b, d andf are (S)—2—chlorobutane. D Structures a, c , and d are (S)—2—chlorobutane. E Structures b and c are (S)—2—chlorobutane. Rationale: Chapter 5 Problem 78 l l - Work out the curved arrow mechanism for the reaction below, which involves a carbocation rearrangement. HO CH3 3 H2804 CH3 + H20 Choose the structure below with curved arrows which CORRECTLY depicts the electron movement involved in ONE of the steps of your mechanism. H30 CHZCH H c 6 E .3 I O (a IN co IOO I-h IU'I A 5 B. 2 C. l D 4 E 3 Rationale: Chapter 4 Problem 64 12- Identify the electrophile and the nucleophile CORRECTLY in each of the following reaction steps. Then figure out how to draw curved arrows which CORRECTLY illustrate the bond—making and bond—breaking processes involved in these reactions. Pick the choice which ACCURATELY describes what is correct and what is wrong about the way in which one of these three reactions is laid out. A + .. . CH-3CH-2CHZCH2 + :Cl : —> CHéCH-ZCIDZCH2 electrophile nucleophile reactlon 1 : Cl : _/\ (V _ . CH-sC:CH + H— Br —’ CH§H_CH2 + Br reaction 2 + electrophile nucleophile — reaction g electrophile nucleophile A. In reaction 1 the electrophile and nucleophile labels are reversed and the curved arrow is drawn backwards. B. Both the curved arrows and the electrophile and nucleophile labels are correctly laid out in reaction 2 . C. In reaction 3 the electrophile and nucleophile are labelled correctly but the curved arrows are drawn incorrectly. D. The curved arrow is correctly drawn in reaction 1 but the electrophile and nucleophile labels are reversed. E. Both the curved arrows and the electrophile and nucleophile labels are correctly laid out in reaction 3 . Rationale: Chapter 6 Problem 27 13- Pick the stereoisomer(s) from below obtained from the reaction of 2—butyne with Na/NH3(liq) followed by Bra/CHZCIZ. CH3 CH3 CH3 H Br Br H H Br B H H Br H Br CH3 CH3 CH3 stereoisomer 1 stereoisomer 2 stereoisomer 3 Stereoisomers 2 and 3 are obtained. Only stereoisomer 1 is obtained. A B C. Only stereoisomer 3 is obtained. D Stereoisomers 1, 2, and 3 are obtained. E Stereoisomers 1 and 2 are obtained. Rationale: Chapter 6 Problem 44b 14. 15. Draw or analyze all of the stereoisomers for each of the compounds named in the multiple choices. Which choice gives the CORRECT number of stereoisomers that exist for the compound named? 1 ,4—dichlorocyclohexane has three stereoisomers. 2,4—dichloropentane has three stereoisomers. A B C. 2,4—dichloroheptane has three stereoisomers. D 3,4—dichlorohexane has four stereoisomers. E 3—chloro—3—methylpentane has two stereoisomers. Rationale: Chapter 5 Problem 34(e,g,h,i,l) Which of the following methods would be the BEST way to prepare the compound having structure 1 shown below? CH-ZCIDH'CH3 CHZCH-CH3 CH-ZCHZCH2 OH 1 2 § __ A. Start with the compound having structure 2 and treat it with Hg(OAc)2 and water followed by NaBH4. __ B. Start with the compound having structure 2 and treat it with BH3/THF followed by HZOZ/OH'. __ C. Start with the compound having structure 3 and treat it with acid (H+) and water. __ D. Start with the compound having structure 2 and treat it with acid (H+) and water. __ E. Start with the compound having structure 3 and treat it with BH3/THF followed by HZOZ/OH‘. Rationale: Chapter 4 Problm 50e 10. 11. 12. 13. 14. 15. Answer Key "Grade or Education" CHEM 2261/01 Summer 10 Exam 2 Chapters 4-6 1 ...
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This note was uploaded on 12/30/2011 for the course CHEM 2261 taught by Professor Crowe during the Fall '08 term at LSU.

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Summ10Ex2 - "Grade or Education" =1 CHEM 2261/01...

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